The present invention relates to valve assemblies for controlling fluid flow, and to pulsator devices constructed with such valves assemblies for producing pulsating type fluid discharges. The invention is particularly useful with respect to the snap-action valve as described in my prior U.S. Pat. No. 6,026,851 (Israel Patent No. 121,380), utilizing a bellows of a construction described in my prior U.S. Pat. No. 5,950,676 (Israel Patent No. 115,969). The present invention is therefore described below with respect to such devices, but it will be appreciated that the invention could also be advantageously used in many other types of devices.
FIGS. 1-3 of the accompanying drawings illustrate a snap-action device constructed in accordance with my prior U.S. Pat. No. 6,026,851 (Israel Patent No. 121,380), including a bellows construction according to my prior U.S. Pat. No. 5,950,676 (Israel Patent No. 115,969). For the sake of brevity, only the pertinent portions of the drawings and the descriptions in the above-cited patents are illustrated and described below with respect to FIGS. 1-3; but for the sake of completeness, the entire contents of the above-cited patents are incorporated herein by reference.
Snap-action valves in general, and the snap-action valve described in the above-cited patents incorporated herein by reference, are characterized by quick and positive movements between their closed and open positions so as to effectively seal the valve opening in the closed position, and to introduce a minimum pressure drop through the valve opening in the open position. Such snap-action valves, when constructed as pulsator devices for irrigation purposes, have been found to be very effective in discharging the water in the form of short, distinct pulses for a wide range of flow rates. It has been found, however, that at very low flow rates, e.g., in the order of 1-4 liters/hr, the pulsator tends to produce drippings between water discharges. Such drippings are undesirable, and sometimes even harmful, since their water content is not effectively distributed with the water discharge and also since they tend to form water pools under the pulsator device.
While such drippings may at times be caused by imperfect sealing of the valve in its closed condition, it is believed that the formation of such drippings, particularly at very low flow rates, is at least partly due to the tendency of the snap-action valve in the pulsator to xe2x80x9chuntxe2x80x9d with respect to its valve-open position. Thus, when the pulsator device uses a snap-action valve, namely one characterized by quick, sharp opening and closing movements, it is believed there is a tendency for the valve to oscillate (open and close) about its opening point. This tendency to xe2x80x9chuntxe2x80x9d about the valve opening point is believed more pronounced in snap-action valves than in slower-action valves where the tendency to xe2x80x9chuntxe2x80x9d is dampened. Moreover, the period of xe2x80x9chuntingxe2x80x9d in a snap-action valve is increased as the flow rates decreases, such that at very low flow rates, the amount of drippings between pulsations outputted by the pulsator device becomes more noticeable.
For example, the snap-action valve illustrated in my above-cited U.S. Pat. No. 6,026,851, as more particularly described below with respect to FIGS. 1-3 of the present application, performs very well in pulsator devices having relatively low flow rates, as low as 10 liters/hr, and even less. However, when the flow rate is reduced to about one or two liters/hr, there is a tendency for the valve to produce drippings accompanying the pulse discharges. These drippings are not only wasteful of the water, but can also be damaging in particular applications of such pulsator devices, such as when used for producing a cooling spray of water in order to prevent undue heating of plants, particularly hot-house plants, at especially hot times of the day.
An object of the present invention is to provide a valve assembly having advantages in the above respects. Another object of the invention is to provide a pulsator device constructed in accordance with such a valve assembly.
According to one aspect of the present invention, there is provided a valve assembly, comprising: a housing defining a main chamber having an inlet connectable to a source of pressurized fluid, and an outlet; a first valve within the main chamber normally closing the main chamber outlet but automatically opening the main chamber outlet in response to a first predetermined pressure within the main chamber; an intermediate chamber communicating with the main chamber outlet; and a second valve having an inlet communicating with the intermediate chamber, and an outlet for discharging fluid from the chambers; the second valve being normally closed but automatically opened in response to a second predetermined pressure slightly higher than the first predetermined pressure, such that the second valve reduces or eliminates drippings in the discharge of fluid from the chambers particularly during low rates of flow of the fluid into the main chamber via the main chamber inlet.
It will thus be seen that the second valve, having its opening pressure slightly higher than that of the first valve, accumulates any xe2x80x9cdrippingsxe2x80x9d from the main chamber outlet in the intermediate chamber until the higher pressure is attained, at which time it is discharges with the water pulses.
Accordingly, even though there may be a tendency to produce drippings, e.g., because of imperfect seals, or because of xe2x80x9chuntingxe2x80x9d of the first valve about its opening pressure particularly at very low flow rates, the xe2x80x9cdrippingsxe2x80x9d from the first valve will be accumulated in the intermediate chamber between the first open valve and the second closed valve, and will therefore be included in the pulse discharge from the pulsator when the second valve opens at the slightly higher opening pressure of the second valve.
The opening pressure of the second valve should be only slightly higher than that of the first valve. For example, if the opening pressure of the first valve is 2 bars, the opening pressure of the second valve may be in the order of 2.1 bars. This slight delay in the opening of the second valve reduces or eliminates the possibility of producing drippings in the discharged water, even during very low rates of flow.
According to further features in the preferred embodiment of the invention described below, the second valve includes a ball, and a spring biasing the ball against a valve seat in the intermediate chamber to close same, the spring being designed to permit the ball to move to an open position with respect to the valve seat in response to the second predetermined pressure.
According to still further features in the described preferred embodiment, the valve assembly is one wherein the chamber outlet includes; a first tubular connector having a transverse wall at one end proximate to the main chamber and formed with the valve seat circumscribing an opening normally closed by the ball of the second valve; the opposite end of the first tubular connector including a second tubular connector formed with an inner annular shoulder; the spring being interposed between the ball and the inner annular shoulder of the second tubular connector and biasing the ball against the valve seat to close the valve opening, the spring being deformable to permit the ball to open the opening automatically in response to the second predetermined pressure being applied to the ball.
As indicated earlier, the invention is particularly useful, and is therefore described below, with respect to the snap-action valve described in my above-cited U.S. Pat. No. 6,026,851 (Israel Patent No. 121,380). In such a valve assembly, the housing is of a bellows construction having a first wall formed with the main chamber inlet, and a second wall formed with the main chamber outlet; the first valve including a deformable membrane fixed to the first wall and normally closing the main chamber outlet in the second wall; the second housing wall being displaceable away from the first housing wall upon an increase in pressure within the main chamber such that the membrane opens the main chamber outlet with a snap-action when the pressure in the main chamber rises to the first predetermined pressure, and closes the main chamber outlet with a snap-action when the pressure in the main chamber drops below the first predetermined pressure.
As also indicated earlier, the valve assembly of the present application is particularly useful in pulsator devices, wherein the outlet of the second valve is coupled to an irrigation device for producing pulsating water discharges therefrom.
Further features and advantages of the invention will be apparent from the description below.